The present invention relates generally to handling and management of RAID-organized recording media in library apparatus, and more particularly to a technique of simplifying and automatizing the handling and management of recording media as subjects of a data striping process.
Library apparatus for handling transportable recording media organized in RAID (acronym for xe2x80x9cRedundant Array of Inexpensive Disksxe2x80x9d) arrays have been known, a typical example of which includes a holder/transporter for holding and transporting a designated recording medium such as an optical disk (hereinafter simply referred to as a xe2x80x9cmediumxe2x80x9d) to a designated place in the library apparatus, a plurality of storage columns having a multiplicity of storage shelves or cells for storing a multiplicity of media, and a plurality of drive devices for writing or reading data to or from a medium inserted therein. The library apparatus also includes a RAID controller for executing a so-called xe2x80x9cdata striping processxe2x80x9d on the media inserted in the plurality of drive devices in a parallel or concurrent fashion. Such library apparatus for RAID-organized media are, so to speak, disk array apparatus where, for each of the storage columns, a designated medium is automatically transported via the holder/transporter between one of the storage shelves and the drive device and where the respective drive devices associated with the individual storage columns are operated in a parallel fashion to perform the data read/write operation on the media inserted therein while executing the data striping process on the inserted media. The above-mentioned RAID controller, which comprises a microcomputer containing a MPU, a ROM, a RAM, etc., controls the transportation of the media by the holder/transporter and also controls the parallel data read/write operations by the drive devices.
In the above-mentioned xe2x80x9cdata striping processxe2x80x9d, one complete data is broken down into a plurality of lower-order units called xe2x80x9cstripe unitsxe2x80x9d each having a predetermined data size such as a bit, byte or predetermined data block, and the thus-obtained stripe units are circulatively delivered to the individual drive devices so that the stripe units are written distributively across a plurality of the media inserted in the drive devices. The data striping process is also performed such that the stripe units are read out from the media, already having undergone the data write operation, so that the read-out stripe units read out from the individual media can be rebuilt together for use as one complete data. In both the data read operation and the data write operation during the data striping process, a plurality of the media to be processed concurrently are regarded as a single medium and therefore accessed simultaneously. By thus operating the plurality of drive devices in a parallel or concurrent fashion, the conventional library apparatus have been attempting to substantially increase a data transmission speed in accessing a large quantity of data. However, reliability of the library apparatus would unavoidably deteriorate as the number of the drive devices to be operated in parallel increases. Thus, more sophisticated disk array apparatus have been proposed, which are intended for achieving higher reliability by employing an information redundancy scheme; for example, duplicate copying of data in the case of RAID level 1, data redundancy by Hamming code in the case of RAID level 2, or data redundancy by parity in the case of RAID level 3. Such disk array apparatus are also called RAID (Redundant Array of Inexpensive Disks) library apparatus.
The known RAID library apparatus are arranged in such a manner that in case a trouble, i.e., an abnormal condition or anomaly such as a malfunction or complete failure, occurs in any one of the media on which the data read/write operation is being performed concurrently, the data and redundancy information are read out from all the other concurrently-processed media and a predetermined data recovery process is performed, on the basis of the read-out data and redundancy information, to recover the data of that medium having got into the abnormal condition.
Although DVDs (Digital Versatile Disks) have been getting more and more popular as high-density digital recording media in recent years, there has not yet been proposed an efficient RAID library apparatus for handling DVD media.
As stated above, the conventional RAID library apparatus perform the data striping process to break down one data into a plurality of stripe units for distributed storage across a plurality of media. Typically, the media to be simultaneously subjected to the data striping process are either randomly selected by a human operator outside the apparatus via a keyboard or other input device or automatically selected by a computer program or the like prestored in a ROM or RAM of the RAID controller. Various pieces of information pertaining to the media simultaneously subjected to the same data striping process, such as information as to in which of the storage shelves the media are being stored, are written into the RAM or the like. Specifically, in the conventional RAID library apparatus, each of the storage shelves has imparted thereto a different or unique physical address as information indicative of the location, in the library apparatus, of that storage shelf. As a consequence, the total amount of the media-pertaining information written in the RAM or the like tends to become enormous, which would significantly complicate management (i.e, address management) of the information pertaining to the media subjected to the data striping process.
Further, in the case where some abnormal condition (malfunctioning or complete failure) has occurred in one of the media during the data striping process, it has been conventional to replace the abnormal medium with a normal medium by manual labor. Also, in order to recover the data written on the abnormal medium, it is necessary to read out the data and redundancy information from one of the normal media having been subjected to the same data striping process as the abnormal medium. To this end, it has been customary to manually take out a necessary substitute medium from one of the storage shelves and insert the taken-out substitute medium into the associated drive device. However, because the information (address) of the storage shelf storing the substitute medium can be acquired only while the library apparatus is turned on or actually in operation, it was not possible to readily obtain such a substitute medium. As understood from the foregoing, the conventional RAID library apparatus achieve a very poor operating efficiency in that once an abnormal condition occurs in one of the media during the data striping process, a great amount of time must be consumed in recovering the data of the abnormal medium and no other processing is permitted until the necessary data recovery is completed. Besides, because the abnormal and normal media can not be distinguished from each other by their appearances, the manual replacement of the abnormal medium with the normal or substitute medium tends to be done erroneously.
It is therefore an object of the present invention to provide a RAID library apparatus and a method of controlling the RAID library apparatus which achieve a greatly enhanced operating efficiency by simplifying management of media and automatizing replacement of an abnormal medium with a normal medium.
It is another object of the present invention to provide a RAID library apparatus and a method of controlling the RAID library apparatus which allow an abnormal medium to be automatically replaced with a normal medium without a human intervention, to thereby avoid an erroneous interchange between the media.
In order to accomplish the above-mentioned objects, the present invention provides an improved media library apparatus which comprises: a transportation mechanism for transporting a transportable medium; a plurality of storage columns having a multiplicity of storage shelves for storing a multiplicity of media; a plurality of drive devices each provided for reading or writing desired data on a selected one of the media; a RAID (Redundant Array of Inexpensive Disks) controller for causing a plurality of the media that are to be subjected to a data striping process to be inserted in the plurality of drive devices and controlling operation of the plurality of drive devices, in a parallel fashion, so as to perform the data striping process on the media inserted in the drive devices; and a controller unit for imparting common addresses to the storage shelves of the plurality of storage columns in corresponding relation to respective predetermined physical locations, within the library apparatus, of the storage shelves in such a manner that each group of the storage shelves of the storage columns lying at a same physical location within the media library apparatus is uniquely identifiable by a particular one of the common addresses, and causing the data striping process to be concurrently performed, by the RAID controller, on the media stored in the storage shelves of the storage columns to which is imparted a specific one of the common addresses.
In the library apparatus arranged in the above-mentioned manner, the controller unit performs control such that the media stored in the storage shelves, to which is imparted a specific one of the common addresses, are subjected to a data striping process; that is, the transportation mechanism is controlled so that the media stored in the storage shelves of the individual storage columns lying at the same physical location are transported thereby to the associated drive devices. If the second address is designated, then the media stored in the second storage shelves from the top of the individual storage columns are taken out and transported to the respective drive devices for the data striping process thereby. Upon completion of the data read/write operation, all the media are transported from the drive devices back to their original storage shelves (i.e., in this case, the second storage shelves from the top of the individual storage columns) for re-storage therein. Because the media stored in the shelves of the individual storage columns, to which the same address is imparted, are subjected to the data striping process, the media designation for the data striping process can be greatly simplified. Namely, according to the present invention, all the media to be subjected to the data striping process can be designated collectively by designation of just one and the same address, without having to designate a different address for each of the storage columns as in the past. By thus grouping the storage shelves of the individual storage columns by use of the common addresses, all the shelves in the library apparatus can be managed with a reduced number of the addresses, and the media having been subjected to the data striping process can be managed in a collective and much simplified fashion.
Further, in recovering the data of the abnormal medium (e.g., malfunctioning or failed medium), it is possible to readily locate another medium on which desired data has been written during the same data striping process as the abnormal medium and which is a non-defective or normal medium corresponding to the abnormal medium. Namely, with the inventive feature that all the media having been subjected to the same data striping process are always stored in the same-address storage shelves of the individual storage columns, so that the user can readily identify the individual media physically and thus readily take out the medium necessary for recovering the data of the abnormal medium.
The present invention also provides a media library apparatus which comprises: a transportation mechanism for transporting a transportable medium; a main storage section for storing a multiplicity of media; a plurality of drive devices each provided for reading or writing desired data on a selected one of the media; a RAID controller for causing a plurality of the media that are to be subjected to a data striping process to be inserted in the plurality of drive devices and controlling operation of the plurality of drive devices, in a parallel fashion, so as to perform the data striping process on the media inserted in the drive devices; a spare medium storage section for storing a spare medium; and a controller unit for, when any one of the media that are being subjected to the data striping process has an abnormal condition, causing the desired data to be written on the spare medium in place of the medium having the abnormal condition.
In case any one of the media that are being subjected to the data striping process is determined as having an abnormal condition, the media library apparatus thus arranged allows the desired data to be written on the spare medium in place of the abnormal medium. Further, the data of the abnormal medium can be written onto the spare medium. Even in the data read operation, if any one medium is determined as having an abnormal condition, the data can be recovered and written onto the spare medium. Namely, once there occurs an abnormal condition in one of the media during the data write operation, the present invention performs the necessary data recovery by assigning a new or spare medium, and thus allows the library apparatus to be used for any other processing immediately after occurrence of the abnormal condition. This means that the data read/write operation can be safely carried on (i.e., the data read/write operation can be automatically adjusted to continue) in spite of the occurrence of the abnormal condition and therefore the library apparatus can be utilized with an increased operating efficiency.
The present invention further provides a media library apparatus which comprises: a transportation mechanism for transporting a transportable medium; a main storage section for storing a multiplicity of media; a plurality of drive devices each provided for reading or writing desired data on a selected one of the media; a RAID controller for causing a plurality of the media that are to be subjected to a data striping process to be inserted in the plurality of drive devices and controlling operation of the plurality of drive devices, in a parallel fashion, so as to perform the data striping process on the media inserted in the drive devices; a spare medium storage section for storing a spare medium; an abnormal medium storage section for storing a medium having an abnormal condition; and a controller unit for, when any one of the media that are being subjected to the data striping process has an abnormal condition, causing the medium having the abnormal condition to be moved over to the abnormal medium storage section to automatically replace the medium having the abnormal condition with the spare medium and carrying on the data striping process using the spare medium.
In the media library apparatus thus arranged, spare and abnormal media are stored in the spare and abnormal medium storage sections, respectively. When there occurs an abnormal condition in any one of the media during the data striping process (data read/write operation), the medium having the abnormal condition is automatically replaced with the spare medium and recovered data is written onto the spare medium having replaced the abnormal medium. With this feature, the media which are the subjects of the data striping process can be effectively managed using the same physical location (address) shared among the storage columns; that is, the management of the media throughout the library apparatus can be greatly simplified according to the present invention.
The media library apparatus of the present invention may further comprise a medium introducing(loading)/discharging (unloading) storage section removably attached to the media library apparatus. In this case, the medium having the abnormal condition is moved out of either the main storage section or the abnormal medium storage section to be then temporarily stored in the medium introducing/discharging storage section so that the medium having the abnormal condition can be discharged out of the media library apparatus via the medium introducing/discharging storage section. Then, a spare medium is inserted into the medium introducing/discharging storage section in order to replenish the media library apparatus with the spare medium and is then moved out of the medium introducing/discharging storage section to be stored in the spare medium storage section.
As noted above, once there occurs an abnormal condition in any one of the media during the data striping process, the present invention automatically replaces the abnormal medium with the spare medium and causes the abnormal medium to be stored into the abnormal medium storage section. Because the automatic medium replacement is no longer permitted if all the spare media are used up, one or more spare media must be stored in the spare medium storage section at any given time. This is the reason why the present invention is arranged to insert a spare medium into the medium introducing/discharging storage section in order to replenish the media library apparatus with the spare medium and also discharge the abnormal condition can be discharged out of the media library apparatus via the medium introducing/discharging storage section. Namely, according to the present invention, the discharge of the abnormal medium discharge and the replenishment of the apparatus with the new normal or spare medium can be conducted collectively without a human intervention, and therefore it is possible to reliably prevent an erroneous interchange between the abnormal medium and normal medium.
According to the present invention, each of the above-mentioned transportable media may be transferred to and from the transportation mechanism and transported by its holder/transporter while being supported on a separate carrying support such as a tray; thus, the present invention can be constructed as a DVD (Digital Versatile Disk) library apparatus. Specifically, in most cases, tray-like carrying supports are provided for disk-shaped media, such as DVDs and CDs (Compact Disks), in a one-to-one relation (i.e., one carrying support per disk), and these disk-shaped media are each stored and, whenever necessary, transported together with the carrying support. Note that the carrying supports may be in the form of cartridges or the like other than the trays.